As Bert says, dismantling and cleaning is the proper way to go.

For Tootler, I'd suggest that if you want to use graphite you should get it from a locksmith or hardware store. While "pencil lead" contains some graphite, in common grades it's actually about 80% hard clay that will scratch, score, and once crumbled in the works will absorb moisture and cause corrosion - or worse.

I bought a new tube of pure graphite a couple of years ago for about a buck ($1 US) only because I couldn't find any of the several 10 to 40 year old ones I know are somewhere handy. NO ONE has ever "used up" a whole tube, and the good stuff is really cheap.

Locksmiths I've talked to seem to differ (among themselves) in their opinions about the wear caused by graphite in locks. It can "cake up" and it's not a perfect lubricant, so you can get some wear debris that binds up the lock. Bad as it is, though, there's not much else you can use in a lock that isn't worse. I have used WD40 to "flush" a stubborn lock (to get the old graphite out), followed by a good shake, some drying, and fresh graphite - but sometimes a 3-pound hammer is about the only thing that works very well at all when a padlock gets really sticky.

John